Load-break fuse switch



July 4, 1950 PlTTMAN 2,514,163

LOAD-BREAK FUSE SWITCH Filed April 12, 1948 IN V EN TOR.

Patented July 4, 1950 UNITED STATES PATENT OFFICE LOAD-BREAK FUSE SWITCHRalph E. Pittman, North Little Rock, Ark. Application April 12, 1948,Serial No. 20,480

1 Claim. 1

This invention relates generally to fuse switches adapted for connectionto electrical circuits, and particularly to a fuse switch constructionsuitable for interrupting load current by appropriate manipulation,which in addition functions as a fuse operable upon predetermined excesscurrent.

Among the objects of the invention may be noted the provision of meansfor manually causing operation of the fuse and interruption of normalload current when desired; the provision of a fuse switch which may beopened and closed as desired without operation of the fuse, togetherwith the automatic overload protection inherent in a fused device. Otherobjects will be obvious or pointed out hereinafter.

The invention comprises the elements and combinations thereof, featuresof construction and arrangement of parts to be exemplified in thedescription to follow, and the scope of the invention will appear in theaccompanying claim.

Fig. 1 of the drawing is a side elevational view of the device, shownpartly in section; Fig, 2 is an end view of the switch. Similarreference characters indicate corresponding parts in the figures of thedrawing.

Load-break switches are well known and widely used in electricalconstruction; fuse constructions are also common. However, in situationsrequiring both interruption of load current and interruption of overloadcurrent, one structure is often supplied for load breaking and anotherand separate structure for overload interruption in response to thefusing of a fusible element. The advantages of accomplishing both ofthese functions by means of a single, simple structure, from thestandpoint of the lower cost of the apparatus in addition to the lowercost of mounting, are obvious.

The manner in which my invention meets the foregoing requirements willbe clear from the following description.

Referring to the drawing, the insulator Ill has secured at its upper endthe upper conducting contact member l3 and at its lower end the lowerconducting contact member 14, to which are respectively attached theline terminal I! and the load terminal I2. A fuse tube 15, of insulatingmaterial, spans the space between the upper end and lower contactmembers, the upper fuse tube contact 26 conductively engaging the uppercontact member 53, and the lower fuse tube contact 21 conductivelyengaging the lower contact memher It.

The fuse link is extends through the fuse tube 15, and electricallyconnects the upper contact member I3 to the lower contact member l4,through its engagement at the button-head end with the upper fuse tubecontact 26, and through the engagement of its outwardly extending endwith the downwardly biased fuse link extractor l8. Within the tube l5,and between the lower open end thereof and the top of the tube, the fuselink 16 is provided with a mechanically weakened fusible element ll, ofsuch tensile strength that the fuse link will rupture at the element llwhen the fuse link is subjected to a predetermined tension.

The fuse tube 15 is mounted on the lower contact member I4 by the pivotl9, and is provided with an eye 20 for convenient opening and closing ofthe fuse switch by means of an insulated switch stick, in whichoperations the upper fuse tube contact 26 disengages the upper contactmember 13 as the tube I5 is rotated on the pivot I9.

At the lower end of the tube l5 and on the lower fuse tube contact 21 ispivotally mounted, for rotation about the pivot 22, the fuse linkrupturing lever 2|. Thi lever includes the arms 24, which straddle thefuse tube 15, and which are joined at their inwardly extending ends bythe laterally extending fuse-extractor engaging portion 25, which is sopositioned that it engages the fuse extractor [8 in its path of movementand urges the latter in the direction to tension the fuse link It whenthe fuse link rupturing lever 2| is urged in counterclockwise directionabout the pivot 22.

Preferably the fuse link rupturing lever 2| extends outwardly anddownwardly from the open end of the fuse tube l5, and is provided with arecess 23 for receiving an insulated switch stick to urge the lever 2|in the direction to rupture the fuse link IS. The dotted lines indicatethe position of the parts immediately after the fuse link rupturinglever 2| has been urged to the position to rupture the fuse link, butbefore the link has been completely extracted from the open end of thefuse tube.

From the above description, it will be seen that the circuit from theline terminal H to the load terminal l2 may be opened in either of twoways as desired, one by pulling the fuse tube l5 to open position, inwhich event only air break circuit interruption is available, oralternately by tensioning the fuse link to rupture, in which event themuch more effective expulsion fuse interrupting ability i utilized.

If the magnitude of the current is such that the arc cannot beinterrupted by air-break, as

may be readily determined by trial, then the fuse link rupturing lever2| may be employed. In so doing, it will be observed that the forceapplied to tension the link to rupture is in the direction to close theswitch. This is a most important consideration from the standpoint ofavoiding unwanted air-break interruption and in addition providingassurance that the switch is in the fully closed position before theblast attending expulsion action is initiated by rupture of themechanically weakened section within the tube. It is in this respectthat the recess 23 is provided, instead of an eye, at the outer end ofthe fuse link rupturing lever 2i.

The end of the fuse link rupturing lever 2i which is intended to bemanipulated to cause breakage of the fuse link preferably extendsoutwardly beyond the pivot 22 for a distance greater than that from theother end of the lever to the pivot, to facilitate breakage of thehigher amperage fuse links which, to handle rated current, areinherently of relatively high tensile strength. In the absence of themechanical advantage so provided, such large amperage links areextremely diificult to fracture.

It will be apparent that changes and modifications may be made in thespecific embodiment of the invention here shown and described and it isintended that the description herein will be regarded as illustrativerather than limiting.

I claim, as my invention:

In a fuse switch having an open position and a closed position, a fusetube open at the lower end and swingable in upward direction formovement from open to closed position, a fuse link within said fusetube, and a pivotally mounted fuse link rupturing lever on said tube atthe open end and arranged to withdraw said fuse link from the open endof said tube in response to a predetermined movement of said lever insaid upward direction, said lever extending respectively inwardly andoutwardly beyond said fuse tube, the inwardly extending portion movingdownwardly when the outwardly extending portion moves upwardly wherebysaid fuse tube is held in closed position while the fuse link iswithdrawn from the open end of said tube.

, RALPH R. PI'I'I'MAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,899,915 Matthews et a1. Feb.28, 1933 2,133,139 Hermann Oct, 11, 1938 2,150,102 Lemmon Mar. 7, 19392,175,328 Walsh Oct. 10, 1939 2,310,466 Schultz et a1 Feb. 9, 1943

